This invention relates to the treatment of dental caries and particularly concerns control of the drilling procedure employed in such treatment.
In many cases, tooth decay extends into the tooth dentin layer, so that a part of that layer must be removed. At the same time, every effort must be made to avoid penetration by the drill bit to the underlying pulp tissue. Heretofore, this has depended entirely on the dentist's skill and judgement.
It has already been proposed to employ resistance measurement to monitor the penetration of an endodontic file to periodontal tissue in connection with root canal therapy. Such a technique is described, for example, in U.S. Pat. No. 3,753,434, which issued to Pike, et al., on Aug. 21, 1973. According to the technique disclosed in this reference, resistance measurements are made while the file is being advanced along a root canal, where it will be in contact with pulp tissue. In the performance of the procedure described in this patent, the tooth dentin is of no concern.
It has also been proposed to monitor the thickness of a tooth dentin layer by measuring the resistance between the upper surface of the dentin layer and a point within the patient's mouth. This is described in FRG-laid-open application 3615632. However, this publication indicates that dentin layers of varying thickness will produce a resistance variation in the range of 10-60 K.OMEGA.. However, applicant has found that the resistance of tooth dentin is between one and two orders of magnitude higher than that range of values.